Damon's maths lesson with Douglas
Matt Damon imagined he was kissing Catherine Zeta Jones - while he was actually snogging her husband Michael Douglas.
The Bourne star locks lips with Michael in their upcoming biopic about the late flamboyant entertainer Liberace, where Matt plays the musician's lover Scott Thorson.
"I kind of think of it in algebra terms, back to my high-school days - it's like the transitive property: by kissing Michael Douglas, I am making out with Catherine," Matt told People.com.
The Good Will Hunting actor did work with Catherine in Ocean's Twelve, but Brad Pitt was the lucky man who got to kiss her.
"I was actually kind of upset that I never got to kiss Catherine, but now I get to kiss Michael. I thought it would have been better if I could have at least kissed them both. I never thought I would get to kiss Michael Douglas," added the father-of-four.
Directed by Steven Soderbergh, the Liberace film - penned by Richard LaGravanese and produced by Jerry Weintraub - has no release date set as yet.